U.S. Ser. Nos. 07/894,851 and 07/895,639 assigned to the same assignee of this application disclose video image display devices for synthesizing and displaying characters and/or title graphics, etc.
The teachings of these prior applications will be described first.
FIG. 5 is a block diagram illustrating a conventional video image display device for synthesizing and displaying digital a character image signal generator circuit portion of the device is shown.
The character image signal generator circuit 15 is provided with a display data RAM 5 for storing a plurality of character codes to be displayed.
In order to write a character code W supplied from a microcomputer 1 to the display data RAM 5, this circuit is provided with a write address register 2 for holding an address signal A out of control/data signals B from the microcomputer 1, a write data register 3 for holding the character code W, a write synchronizing signal S according to the control signal therein, an address selecting circuit 6 for generating an address signal U directed to the display data RAM 5 upon receiving the write signal S from the write synchronizing circuit 4.
In order to read a display character code G from the display data RAM 5, the character image signal generating circuit 15 is provided with a vertical address counter 12 for generating a line selecting signal R upon receiving a vertical synchronizing signal H from a synchronizing signal generating circuit 11 for generating a dot clock D upon receiving the horizontal synchronizing signal H. The character image signal generating circuit 15 is also provided with a horizontal address counter 10 for generating a column selecting signal C upon receiving the horizontal synchronizing signal H and the dot clock D and applying the column selecting signal C to the address selecting circuit 6 and the write synchronizing circuit 4.
In order to display a pattern of the character code thus selected, the character image signal generating circuit 15 is further provided with a character generator 7 for generating a character pattern P equivalent to one line out of the pattern equivalent to one character upon receiving an address signal L generated in the address selecting circuit 6 and the character code G thus selected serial converter circuit 8 is provided for sequentially outputting a character pattern having a plurality of bits corresponding to one line dot by dot through the dot clock D. The output signal of the serial converter circuit 8 is combined with another image signal E before being applied to CRT 9 on which a superimposed image is displayed.
A camera integrally combined with video and having a large scale liquid crystal display device as a monitor has been commercialized recently. Such camera will be referred to as "liquid crystal monitor movie" hereinafter. In such liquid crystal monitor movie, a camera portion and a display device can be inverted mutually, so that a user can take a picture of himself by inverting the camera portion and display it on the display device. In a TV telephone, both talkers are displayed on a screen.
When a user himself is to be displayed his right side is shown on the left left and is not shown as a mirror image. In order to make it a mirror image in such video image display device, a function is given to the liquid crystal display device for displaying an image obtained when a video camera portion by converting it into a mirror image. The reason for providing such a mirror image converter circuit on the side of the liquid crystal display device is that it is necessary to record an image signal on a video tape in normal condition.
Thus, it is possible to obtain the same image as the user's mirror image and there may be no unnatural feeling. However, when a displayed image is converted into the mirror image, characters to be superimposed are also converted into their mirror image, which is unnatural.
In order to solve such a problem, two kinds of character generators are provided conventionally. One of them produces symbols and characters which correspond to a usual image and the other produces mirror images of symbols and characters. When the video camera is directed to the user, the character generator producing mirror image characters and/or symbols is selectively used. The mirror image characters and/or symbols are combined with the video image and the combined image is then mirror image converted, so that normal characters and/or symbols are superimposed on the mirror video image.
In such conventional video image display device, however, two character generators must be provided. Each character generator requires a large memory capacity due to the fact that characters and/or symbols are stored in bit pattern. Therefore, when two character generators be provided in an IC, its integration area becomes so large that other function circuits can not be integrated therein.
Further, there may be limitation of IC area in which character generators can be integrated in view of other integrated circuits. Therefore, when such function as displaying mirror image is added to the device, the number of ICs to be mounted on the video image display device is increased.